(i) Field of the Invention
The present invention relates to an operation detection switch for use in detecting an operating portion of a musical instrument being operated.
(ii) Description of the Related Art
A typical conventional operation detection switch for detecting an operating portion of a musical instrument being operated comprises a switch main body disposed between the operating portion of the musical instrument and the surface of a circuit board having a first and a second fixed contacts formed thereon, and a first and a second movable contacts corresponding respectively to the first and the second fixed contacts. The first and the second movable contacts are provided on the switch main body.
In a keyboard instrument such as an electronic piano or an electronic organ, for example, the first and the second fixed contacts are formed in sequence along the length direction of each key as an operating portion of the keyboard instrument, and the operation detection switch is disposed so as to face the surface of the circuit board. In accordance with the depression of the key, the switch main body, which is directly or indirectly pressed by the key, pivots around one end of itself as a fulcrum point, with the result that the first movable contact abuts the first fixed contact, then the second movable contact abuts the second fixed contact. FIG. 12A is a graph plotting the stroke in abscissa and the state of action (ON or OFF) of the switches s1 and s2 constituted by the first and the second movable contacts in combination with the first and the second fixed contacts, respectively, in ordinate.
In the keyboard instrument, sound parameters (e.g. volume, tone) corresponding to the depressing action are determined based on the required time period from when the first movable contact abuts the first fixed contact until when the second movable contact abuts the second fixed contact, then the sound having the determined parameters is output from a loudspeaker or the like.
In the case of using such a switch, however, a depressing action of the key can be detected only at two reference timing points, i.e., when the first movable contact abuts the first fixed contact and when the second movable contact abuts the second fixed contact. Accordingly, as long as the time period between the above two reference timing points when the depressing action is detected is the same (see FIG. 13A: t1=t2=t3), the same parameters are determined regardless of whether or not the speed of the key depression has changed in the middle of the action. Therefore, the manner of performance in which the speed of depressing the operating portion changes in the middle of the action cannot be covered.
A recent solution to this problem is to detect the depressing action of a key by using an operation detection switch provided with a first, a second and a third movable contacts for abutting a first, a second and a third fixed contacts, respectively, which enables detection of the depressing action of the key at three reference timing points. By this, even in the case where the total time period required to detect the depressing action, i.e. the time period from the first to the third reference timing point, is the same (see FIG. 13B: t1=t2=t3), sounds having different parameters can be determined if the time period between the respective two reference timing points is different (see FIG. 13B: t11≠t21≠t31, t12≠t22≠t32). Therefore, the manner of performance in which the speed of depressing the operating portion changes in the middle of the action can be covered. FIG. 12B is a graph plotting the stroke of the key while being depressed in abscissa and the state of action (ON or OFF) of the switches s1, s2 and s3 constituted by the first, the second and the third movable contacts in combination with the first, the second and the third fixed contacts, respectively, in ordinate.
However, the operation detection switch having three movable contacts involves a problem that the manufacturing cost of the operation detection switch itself is increased due to the increased number of movable contacts compared with an operation detection switch having only two movable contacts. Furthermore, three fixed contacts must be formed on the circuit board, which inevitably increases the manufacturing cost of an entire musical instrument.
The object of the present invention is to provide an operation detection switch and a musical instrument that can cover the manner of performance in which the speed of depressing the operating portion changes in the middle of the action, while requiring a reduced manufacturing cost compared with a prior art operation detection switch and a musical instrument. Another object of the present invention is to provide a parameter determination program available for such a musical instrument.